[minnesota_bound]

The U.S. Navy has some 4,000 Tomahawks.
http://www.defenseone.com/business/2017/04/us-about-stop-buying-tomahawk-missiles-ones-hit-syria/136866/

The Chinese or some other enemy would use their missiles on the approaching fleet. I would think they have as many or more if war is coming.
Our subs need to be converted to fire many more missiles then they do now to take out theirs prior to the navy ships getting close but that would be difficult as they can be on land or sea or air platforms. Their iPhone factories would be converted to making iMissiles by the thousands.

[central_va]

The simple answer is you stay offshore at the maximum range of the threat until the ASM missile threat is neutralized. If the range is 1,000 NM then stay that for away. At 1,000 nm you get a 1 1/2hour (90 minutes) warning. You've never been in the Navy have you?